Engineering resources
Building a stack-up approval drawing
A stack-up approval drawing is the agreement between the electrical design and the physical board construction. It should let a reviewer identify every copper layer, dielectric interval and unresolved tolerance without searching through a quotation. For an Arlon PCB, exact material designations also need to follow those layers.
Give each row one physical meaning
Number copper layers from the top of the board. Between them, describe the core or bonding interval and state whether its thickness is nominal starting material or a finished requirement. Mark signal and plane functions separately from the material name. Reference-plane continuity deserves its own review: Texas Instruments’ high-speed layout guidance discusses how discontinuities in planes affect return paths. A mechanically plausible stack does not establish electrical suitability.
Use three status columns: design target, fabricator proposal and approved value. A blank approved column means the issue remains open. This simple distinction prevents a preliminary quotation stack from becoming a production instruction merely because somebody attached it to an email.
A thickness budget with visible assumptions
Hypothetical arithmetic example, not a manufacturable stack recommendation. Suppose a proposed four-layer section contains two 0.180 mm dielectric intervals and a 0.900 mm central core, with four copper layers provisionally represented as 0.035 mm each. The simplified sum is 0.180 + 0.900 + 0.180 + 4 × 0.035 = 1.400 mm. This excludes solder mask and finish and assumes each copper entry describes the relevant finished thickness.
If the mechanical requirement is 1.600 mm, the 0.200 mm difference is an unresolved design item. Do not simply add it to one bonding interval. The revised construction must also satisfy impedance, material availability and fabrication review. Put the acceptance measurement method beside the final thickness requirement.
| Drawing field | Question answered | Approval evidence |
|---|---|---|
| Layer identifier and function | Where does each signal reference? | Layout and stack revision agree. |
| Material and construction | What core or bonding system occupies the interval? | Named grade and proposed construction reviewed. |
| Dielectric and copper dimensions | What will be modeled and what will be inspected? | Finished values and tolerances defined. |
| Impedance table | Which structures have controlled targets? | Target, tolerance, geometry and coupon plan agreed. |
Control changes after approval
Require a new review when a dielectric thickness, material, copper definition or signal reference changes. Keep the old proposal in the project archive but clearly mark it superseded. A purchasing order should point to one approved stack revision, not a folder containing several plausible versions.
Before signing, reconcile the stack-up with the board outline, via structures and fabrication requirements. Compare material designations against the material library. Record the approving people or roles and the date; unresolved assumptions belong in a separate issue list with an owner.
Discuss your fabrication package
Submit project requirements and fabrication files for review. Material suitability, availability and commercial terms require project-specific confirmation.
Sources and scope
Manufacturer references checked 9 October 2026. Examples and review worksheets are original editorial guidance, not approved process instructions. Historical reference documents are used for fundamentals, not current product availability.